DESCRIPTION

ALTER DOMAIN changes the definition of an existing domain.
There are several sub-forms:

SET/DROP DEFAULT

These forms set or remove the default value for a domain. Note
that defaults only apply to subsequent INSERT
commands; they do not affect rows already in a table using the domain.

SET/DROP NOT NULL

These forms change whether a domain is marked to allow NULL
values or to reject NULL values. You can only SET NOT NULL
when the columns using the domain contain no null values.

ADD domain_constraint

This form adds a new constraint to a domain using the same syntax as
CREATE DOMAIN [create_domain(7)].
This will only succeed if all columns using the domain satisfy the
new constraint.

DROP CONSTRAINT

This form drops constraints on a domain.

OWNER

This form changes the owner of the domain to the specified user.

SET SCHEMA

This form changes the schema of the domain. Any constraints
associated with the domain are moved into the new schema as well.

You must own the domain to use ALTER DOMAIN.
To change the schema of a domain, you must also have
CREATE privilege on the new schema.
To alter the owner, you must also be a direct or indirect member of the new
owning role, and that role must have CREATE privilege on
the domain's schema. (These restrictions enforce that altering the owner
doesn't do anything you couldn't do by dropping and recreating the domain.
However, a superuser can alter ownership of any domain anyway.)

PARAMETERS

name

The name (possibly schema-qualified) of an existing domain to
alter.

domain_constraint

New domain constraint for the domain.

constraint_name

Name of an existing constraint to drop.

CASCADE

Automatically drop objects that depend on the constraint.

RESTRICT

Refuse to drop the constraint if there are any dependent
objects. This is the default behavior.

new_owner

The user name of the new owner of the domain.

new_schema

The new schema for the domain.

NOTES

Currently, ALTER DOMAIN ADD CONSTRAINT and
ALTER DOMAIN SET NOT NULL will fail if the named domain or
any derived domain is used within a composite-type column of any
table in the database. They should eventually be improved to be
able to verify the new constraint for such nested columns.